Question

An element with a mass of 680 grams decays by 24.2% per minute. To the nearest minute, how long will it be until there are 10 grams of the element remaining?

(Im in 9th grade)

Answer 1

4 Minutes. (Approx, to the nearest minute)

Explanation:

24.2% of 680 is: 164.56

164.56 * 4(Minutes) = 658.24

164.56 * 5(Minutes) = 822.8

So since it's rounded up, 5 minutes is too long because it would be long gone by then, and the next highest amount of minutes that it can decay for but not reach LESS than 10 grams left, is 4 minutes.